I converted a Spot Ajax usng a 750 watt Bafang bottom bracket motor...48v 11ah battery.

it weighs 40lbs, with battery. It runs for about 2 hours riding time... A shorter average ride would mean using a smaller and lighter battery... Putting weight around 37lbs.

it can go up 20% grade hills at 15 mph with easy pedal effort... It will run at 25 on level ground no pedalling at all.